What is "pro-drop language"

n. A language that leaves out certain pronouns in situations usually specific to the language or language family, such as Spanish and Persian which frequently drop subject-form pronouns.

A pro-drop language (from "pronoun-dropping") is a language in which certain classes of pronouns may be omitted when they are in some sense pragmatically inferable (the precise conditions vary from language to language, and can be quite intricate). The phenomenon of "pronoun-dropping" is also commonly referred to in linguistics as zero or null anaphora.

In everyday speech there are often instances when who or what is being referred to can be inferred from context. Proponents of the term "pro-drop" take the view that pronouns which in other languages would have those referents can be omitted, or be phonologically null. Among major languages, two of which might be called a pro-drop language are Japanese and Korean (featuring pronoun deletion not only for subjects, but for practically all grammatical contexts). Chinese, Slavic languages, and American Sign Language also exhibit frequent pro-drop features. Non-pro-drop is rather an areal feature of Standard Average European including French, German, and English.

Some languages might be considered only partially pro-drop in that they allow deletion of the subject pronoun. These null subject languages include most Romance languages, with French being the most notable exception, as well as all the Balto-Slavic languages and to a limited extent Icelandic.